Electrical pin jacks



United States Patent M 3,506,948 ELECTRICAL PIN JACKS Richard U. Clark, South Lyndeboro, N.H. Filed Oct. 12, 1967, Ser. No. 674,964 Int. Cl. H01b 17/26; H011 9/12 US. Cl. 339-426 3 Claims ABSTRACT OF THE DISCLOSURE The electrical pin jack constituting the present invention comprises a thin walled, knurled, non-bifurcated, distensible, cup-like metal tube having a pin termination at one end. By virtue of the knurling of the cup section this area becomes work hardened and of spring-like consistency also a transverse cross-section of the cup wall would show a minor wave like configuration which under internal pressure, caused during use by the insertion of a tight fitting co-operating conductor pin of round cross-section, would tend to stretch out or distend same thus providing for complete mating of cup and pin to form a very low resistance electrical connection. The closed end of the cup section terminates in a rod configuration to provide for a fixed electrical connection and the periphery of the jacks metal area is encased in a pliable bushing of insulating material to facilitate mounting the jack in a hole in a panel. A push-on nut on the rod area permits compression of the bushing and generates an inward radial pressure at the panel hole contact area to augment the spring grip between jack cup and conductor pin.

The present invention has to do with improvements in pin jacks of the type that are normally mounted in a nonconducting bushing especially the style of bushing outlined in my US. Patent No. 3,166,634.

One of the objects is to provide in my present invention a partially hollow tubular spring contact which can receive and hold a connecting pin with a friction grip without the need for maintaining a close tolerance force fit between pin and jack.

Another object is to provide a hollow metallic shell type of jack combined with a solid continuing cylindrical section or shank which latter can be used as an anchor point at which to solder a wire lead. Additionally said pin jack can be inserted into a plastic bushing or grommet of the type described in my Patent No. 3,166,634 and it will then be possible to fit the solid section or shank of the jack with a spring push nut that can be adjusted so as to compress the plastic bushing within a hole in a panel or case by sliding said nut along the shank to compressively contact the bushing. A force fit threaded nut may replace the push nut if selected to give a locked in place grip when forced along the shank so as to abut and compress the bushing.

My main object is to obtain a spring contact eifect as a function of a partially hollow pin of circular cross-section of such a design that when it is used encased with a suitable resilient bushing as an axial through member and the latter is compressively mounted in a suitable panel, in a closely fitting hole, the hollow section of said pin will be slightly compressed. The resilient member may be of insulating or of conducting material, depending upon the type of material of the panel it is to be used in, and the hollow section of the pin, encased, takes on the nature of a spring loaded receptor or jack.

When my jack is fitted with a supplementary resilient conductive member and in some cases additionally within a rigid conducting member it may be mounted in a panel of electrically insulating material to increase its tolerance to a mating conductor pin, or when not so used it may be axially mounted in a resilient plastic bushing for subsequent mounting in a hole in a metal case.

A still further object of my invention is to supply a device in which the jack contact can be readily made in production with very low cost tooling on an automatic screw cutting lathe whereas if made as a stamping or an extruded or cold headed part it would require tooling of very impressive cost and a costly secondary operation would be needed to complete the part. My new special configuration and method of pin mounting in a resilient member also results in very long spring contact life. An added important advantage of my form of jack conductive member is that no slotting or cutting of the contact section is required to give the spring jack effect.

In working out my invention I have found that by knurling one end of a brass pin and then drilling axially into the end within the knurl, to form a very thin walled tubular section, there resulted a spring contact effect within the tube which was amplified when the outside wall was compressed with a resilient casing. This casing may be in several forms and materials as outlined later. An added advantage in making my jack member as a knurled tube is that the knurling operation imparts to the metal tube a spring temper by work hardening same. In practice half hard brass parts become hard brass from the process of work hardening due to knurling.

The knurled section of the pin need only cover a width of one sixteenth to one eighth of an inch or so and should not run all the way to-the open end of the hollow section as this will result in a reinforced rim at the orifice of the jack section of the pin. This unknurled section may if desired be fashioned in the form of a flange for added strength. For the knurled section I prefer a plain bar type rather than a diamond knurl.

When a plain or bar type knurl is employed and the knurled section of the pin drilled out, the wall thickness at the trough of the knurl should be reduced to almost foil like thickness but be reinforced by the web like bars of the knurl which bars impart a spring effect to the drilled and knurled section.

The actual wall thickness of the hollow section of the jack between the knurl bars in my novel jack will depend somewhat on the type of resilient bushing in which it is mounted. In the case of a jack to mate with a conducting pin or plug having a diameter of forty thousandths of an inch a tube wall thickness at the trough of the knurl will be in the order of from two to four thousandths of an inch, if jack is plastic encased.

My novel basic jack device has been evolved primarily for axial insertion into a resilient bushing but it may also be encased in a metal tube which is lined internally with one or two convolutions of spring wire mesh. Using this type of structure the knurled section of the basic jack, once inserted in the mesh is resiliently compressed by the spring wire mesh. The whole device may them be mounted within a non-resilient insulating bushing or panel.

A preferred form of my resilient plastic jack holding bushing would be made of polytetrafluoroethylene which material has an inherent memory characteristic this plastic having a durometer hardness in the order of fifty to sixty five on the Shore D scale.

Turning now to the drawing which forms a part of this application there is shown in FIGURE 1 an end view of the hollow pin jack of the type obtaining its spring contact effect from a wrap of two convolutions of spring wire mesh held inside of a plain metal tube.

FIGURE 2 shows a partial cross-sectional longitudinal view of the item of FIGURE 1 showing two convolutions of spring wire mesh but with the knurled thin walled jack tube broken oil and partially removed.

FIGURE 3 shows my preferred form of pin jack mounted in a resilient plastic bushing, the latter being shown as a center section cut parallel to the axial jack encasing hole. This bushing is made of plastic having a memory characteristic and it encases the hollow knurled jack pin and the latter is shown in elevation. The panel for mounting the bushing in is shown in cross-section of the thickness.

FIGURE 4 is a detailed view of the jack contact member 8 of FIGURE 3, showing also shank 8a.

Referring again to FIGURE 1 there is shown at lead line 1 a partially hollowed metal pin with a flange at one end. Within the hollow section of said pin is shown a wire mesh tubing consisting of two layers at lead lines 3 and 2. Coaxial with said wire mesh tube is shown a thin walled metal tube having a knurled exterior wall at 6. This latter tube may be of work hardened brass, beryllium, copper or the like. A tab for retaining the mesh tube is shown at 5 and the butting ends of the mesh tubes at 7.

FIGURE 2 shows the partially hollowed metal pin at 1 in partial longitudinal cross-section and two convolutions of wire mesh tube in partial cross-section and par tial elevation at 2 and 3. The thin walled externally knurled tube 6 of FIGURE 1 having its top broken off as at 13 and having been partially removed. There is also shown a groove 4 to provide a point for a wrapped wire connection. There is further shown a tab 5 fashioned to secure the mesh section of the jack.

FIGURE 3 shows the thin walled knurled tube and pin in elevation at 8 co-axial with a plastic bushing 9 which latter is shown in cross-section. The broken lines 12 represent the internal impressions of the troughs of the external knurling. There is further shown at 10 a suitable push nut holding the pin axially within the plastic bushing. The bushing is shown as having a flange and a barrel. There is also shown at 11 a panel in which the bushing is mounted.

FIGURE 4, a detail view of a part 8 FIGURE 3, shows a random cross-section of a corner of the knurled jack tubes open end to more clearly illustrate why the knurled section has resilience due to the wave-like distortion of the Wall of the tube section at 12.

When the jack and bushing are mounted in a panel and the push nut 10 is moved up so as to compress the plastic bushing there will be a resultant pressure on the thin knurled wall of the jack which results in reducing slightly the bore diameter of the knurled section of the jack and holding it thus under the resilient pressure of the plastic bushing.

In the jack form shown in FIGURE 1 the constricting resilient pressure is supplied by the spring wire mesh convolutions that encase the thin walled knurled tube which latter is force fitted into the wire mesh liner.

As mentioned in the second paragraph of this specification my jack pin is intended to be used with connecting pin or plug and said pin in practice is made with a chamfered or rounded leading end. This allows the pin to be inserted in the constricted jack tube and cause it to expand slightly during insertion thus providing a desired tight fit as the pin is pushed completely into the jack. This tight fit is maintained as a result of the pressure of the resilient bushing that is exerted upon the knurled section of the jack. When the conducting pin is removed the bore of the jack again becomes slightly constricted.

Having described my invention, I claim:

1. In combination a metallic, electrically related jack for cooperating with a metallic connecting pin of constant lateral cross-section and symmetry, said jack comprising a thin walled, non-bifurcated, externally knurled,

readily distensible, cup-like conductive section having radially oriented, spring-like characteristics acting throughout the unbroken periphery of said cup-like section and a continuing solid section extending from said cup and a jack encircling bushing like container having contractile characteristics and arranged coaxially with and in compressive contact against the outer periphery of all knurled sections of said non-bifurcated cuplike jack whereby the radial spring-like characteristics of the cup-like jack section is augmented.

2. A device as in claim 1 in which the metallic electrically related jack is initially compressively encased within a resilient metallic tubular member and both members subsequently mounted axially within the encircling bushing like-container of claim 1, the encasing tubular member containing one or more convolutions of spring Wire mesh.

3. A device as in claim 1 for compressively mounting in a hole in a panel in which the knurled cup-like section extension is rod-like in form and said jack encircling bushing-like container comprised of by a memory conscious plastic, the cup-like section and rod-like solid jack section extension being inserted coaxial with the bushing and a. push nut affixed thereto, said r0d-like extension and said nut being adapted to compress the memory conscious container by moving said nut into pressure contact with said memory conscious container thereby exerting inward pressure on the container and the cup-like section where it passes through the hole in the panel.

References Cited UNITED STATES PATENTS 2,189,987 2/1940 Kellems 33963 3,166,634 1/1965 Clark 174-18 X 3,193,895 7/1965 Oxley 339126 X 3,292,132 12/1966 Murphy 339221 X FOREIGN. PATENTS 696,793 10/ 1930 France. 1,063,811 12/ 1953 France.

RICHARD E. MOORE, Primary Examiner U.S. Cl. X.R. 

